Popular electronic devices include tablet computers, electronic book readers, and smartphones. Such electronic devices typically include a housing assembly coupled to the cover glass of a display assembly. In a commonly used housing assembly design, three separate mechanical chassis parts—a mid-frame, a rear cover, and a front cover—are joined to form the housing assembly. Most of the electronic components within the device, including the main printed circuit board (PCB) and the liquid crystal display (LCD) module, are attached to the mid-frame with screws. Next, the touch-sensing panel is attached to the front cover, and then the mid-frame with electronic components already mounted on it is attached to the front cover with additional screws. Finally, the rear cover is attached to the front cover to enclose all of the components. The mid-frame must have a fairly high structural rigidity in order to support all of the components which are attached to it before the mid-frame is attached to the front and rear covers. This typically requires that the mid-frame be formed out of a relatively thick metal frame, thereby increasing size and weight. This design is advantageous because the rear cover can be removed to easily access the various components for re-working or repair, but the use of three parts to form a housing assembly increases the overall parts count and may, therefore, increase manufacturing costs.
In many devices currently on the market, the housing assembly includes injection molded plastics formed onto metal chassis components. These plastic moldings can provide increased stiffness to the housing and may also provide an improved external appearance of the device by covering less aesthetically pleasing structures, such as a bare metal chassis. However, thick layers of plastic molding material increase the weight and thickness of the device.
Device manufacturers are constantly searching for ways to reduce manufacturing cost, decrease the size and weight of the mechanical chassis components, and improve the aesthetic appearance of the device. Accordingly, there is a need for improved housing architectures for electronic devices.